MRI of the Brain and Spine
Order MRI of the brain and spine without IV contrast as the next diagnostic step. 1
Clinical Reasoning
This patient presents with acute-onset slurred speech (dysarthria) lasting 6 hours with a prior similar episode that resolved, plus focal neurological findings (dysmetria and leg hypertonicity) on examination. The combination of recurrent transient neurological symptoms with persistent focal deficits and an unremarkable CT head demands further investigation with MRI.
Why MRI is the Appropriate Next Step
The American College of Radiology recommends MRI for patients with new focal neurological deficits lasting longer than 6 hours, with an appropriateness rating of 8/9 (usually appropriate). 1
MRI is significantly more sensitive than CT for detecting acute infarcts, small ischemic lesions, demyelinating disease (such as multiple sclerosis), and other subtle neurological pathologies that can present with recurrent transient symptoms. 1, 2
For patients presenting with recurrent episodes of slurred speech and mild dysarthria with focal neurological findings (dysmetria, hypertonicity), MRI head without IV contrast is the most appropriate diagnostic test. 1
Specific MRI Protocol
Begin with MRI brain and spine without IV contrast as the initial study. 1
Consider adding gadolinium contrast if demyelinating disease (multiple sclerosis), infection, or tumor is suspected based on initial findings. 1
Include MRA (magnetic resonance angiography) of the head and neck to evaluate for vascular abnormalities, which has an appropriateness rating of 8/9 for patients with TIA-like symptoms. 1
Spinal cord imaging is equally valuable when brain imaging alone may be nondiagnostic in patients with suspected demyelinating disease—some MS patients have minimal or no brain lesions but significant spinal cord involvement. 2, 3
Why Other Options Are Inappropriate
CSF analysis: Not indicated as the initial next step without first visualizing structural pathology on MRI. CSF analysis would be considered after MRI if demyelinating disease or infection is suspected based on imaging findings.
Screening (unclear what this refers to): Too vague and does not address the acute need for neuroimaging in a patient with focal neurological deficits.
CEEG (continuous EEG): Not appropriate here—the patient has focal motor and coordination findings (dysmetria, hypertonicity) rather than altered consciousness or suspected seizure activity.
No further testing: Unacceptable given the presence of focal neurological deficits and recurrent symptoms. Relying solely on CT imaging for transient neurological symptoms can miss subtle pathology, particularly small ischemic lesions, demyelinating plaques, or early infarcts. 1
Critical Differential Diagnoses to Consider
The clinical presentation suggests several possibilities that MRI can differentiate:
Multiple sclerosis or other demyelinating disease: Recurrent episodes with complete resolution followed by persistent deficits, cerebellar signs (dysmetria), and upper motor neuron signs (leg hypertonicity) are classic. MRI is the most sensitive method for revealing dissemination of white matter lesions in space and time. 2
Posterior circulation ischemia/TIA: Recurrent transient symptoms involving speech and coordination could represent vertebrobasilar insufficiency or small vessel disease. MRI detects acute infarcts with far greater sensitivity than CT. 1
Spinal cord pathology: The leg hypertonicity suggests possible spinal cord involvement, which would be missed on brain imaging alone. 3
Common Pitfalls to Avoid
Delaying appropriate imaging when neurological symptoms are present can miss treatable conditions such as acute stroke or demyelinating disease. 1
Relying on a normal CT scan to rule out significant pathology in patients with focal neurological deficits—CT has poor sensitivity for acute ischemia, small lesions, and demyelination. 1
Failing to image the spine when brain MRI is nondiagnostic but clinical suspicion for demyelinating disease remains high—approximately 5-10% of MS patients have minimal or no brain lesions but significant spinal cord involvement. 3